1. Field of the Invention
This invention relates to a process and method of raising manholes in sewer construction and street and highway resurfacing projects, and more specifically, to a process for obtaining a complete seal between the raised manhole and the upper edge of a sewer catch basin opening when a manhole is raised to a new grade level required by street repaving or installation of a new street or sewer catch basin.
2. Description of the Prior Art
Municipal governments are responsible for thousands of dollars in property damage and personal injuries suffered as a result of improperly installed or improperly maintained manholes, which provide access to municipal storm and sanitary sewers, and to public utilities. Improperly installed or maintained cast manhole frames cause damage to automobiles and bicycles and are sources of legal headaches for many administrators and elected officials of a municipal government.
Improperly installed or maintained manholes are also costly to the tax payer, in that such improperly installed or maintained manholes allow excessive amounts of surface and sub-surface water to flow into the storm and sanitary sewers of a city, resulting in additional costs for wastewater treatment facilities for handling the excessive water flow entering the system through the improperly installed or maintained manholes.
Improperly installed or maintained manholes are today costing many communities considerable additional expenses, which would be unnecessary if the storm and sanitary manholes were properly installed and maintained. This increase in costs of operation of storm and sanitary sewage systems is especially important today with the new Environmental Protection Agency (E.P.A.) regulations that now require Inflow/Infiltration (I/I) and Sewer System Evaluation Surveys (S.S.E.S.) to be made by municipal governments on municipal storm and sewage treatment facilities.
In the ideal situation, all manholes in a storm or sanitary system should be functional, because they are the only access point to the interior of the storm or sanitary sewer system. A properly constructed and maintained manhole must have its lid level with the surface of the street or ground. This keeps the manhole accessible, so that inspections and repairs are easily made, thereby adding to public safety.
In addition, a manhole must be accessible in order to maintain the manhole and sewer system and meter the flow there through.
However, many manholes are not functional, nor are they accessible. Many are buried under asphalt, gravel or sidewalks in a city. Other manholes have not been adjusted to the proper grade level as new layers of asphalt or concrete have been placed on the surface of a street. Such improper maintenance of a manhole results in a bump or a hole in the road pavement.
The solution to these problems is to readjust the manhole frames to the proper grade of the street. Such readjusting of the manhole frames to the proper grade level of the street is presently done by cutting away the pavement around the manhole frame and removing the subsoil from around the manhole frame and the upper surface of the sewer catch basin.
The cast manhole frame is then raised and shimmed to the proper level by placing bricks at three equidistant points around the circumference of the manhole frame. The space between the bottom edge of the manhole frame and the upper edge of the catch basin opening is then filled with bricks, which are, in turn, mortared together, at their joints. Such a process is very time consuming, in that the bricks must be put in place one at a time by hand, and the joints must be thoroughly mortared in order to prevent leakage between the manhole frame and the sewer catch basin.
The exterior surface of the brick and mortar collar must also be sealed to strengthen the collar and prevent the bricks from caving in from exterior pressure from the subsurface dirt, water and surface paving.
Another method has been developed in an effort to save labor costs in raising a manhole frame to the proper grade. This process incorporates the standard method of leveling the manhole frame by placing bricks at three points equidistant around the circumference of the frame to obtain the proper grade level. However, instead of bricking the space between the manhole frame and the top of the catch basin by hand, thick concrete is poured around the exterior of the manhole frame and upper edge of the sewer catch basin. The concrete is of a sufficiently thick consistency, so as to prevent it from readily flowing into the open space between the manhole frame and the sewer catch basin. However, at least one man is required to try to keep the concrete from flowing into the interior of the catch basin. This, of course, is not very successful, as the concrete will drop away from the vertical surface and fall into the interior of the catch basin. Furthermore, a very irregular, uneven interior surface results from this method, which is totally unsatisfactory.
A third, less used method, is to use precast concrete rings instead of bricks to close the space between the upper surface of the sewer catch basin and the lower edge of the manhole frame. However, this method is very expensive, and creates many problems with regard to the leveling of the manhole frame. Furthermore, the precast concrete rings are available only in certain sizes and, thus, do not lend themselves to every application.